In the HIV infected neonate, opportunistic infections may develop in children with normal T-lymphocyte subset number and even in the absence of an inverted CD4/CD8 ration. Recent studies have suggested that these critical differences may be related to alteratios in cytokine production. We propose to evaluate: 1. shifts in lymphocyte subpopulations specificallysubpopulations of CD8+ cell subsets and CD4+T cell. 2. Responsiveness to immune system activators specifically Interleukin-2, as reflected in proliferation, expression of the IL-2 receptor, IL-2 production, and HIV viral activation. 3. Serum levels of prostaglandin, (PGE-2) which may cause down regulation of the cytokine network. 4. The ability of lymphocytes form HIV exposed infants to mediate natural killer (NK) activity in vitro.